Refinement of Bouwer‐Rice Baildown Test Analysis

Abstract The recoverability of light nonaqueous phase liquids ( LNAPL ) in the subsurface can be estimated using LNAPL transmissivity. LNAPL transmissivity is analogous to aquifer transmissivity in that it represents the volume of LNAPL that flows through a unit width of a porous medium for a unit gradient in a unit time. Methods for estimating LNAPL transmissivity from baildown test data have been modified from the Bouwer and Rice (1976) slug test method by Lundy and Zimmerman (1996) and Huntley (2000). The primary assumptions when estimating LNAPL transmissivity with the Bouwer‐Rice method include, a quasi‐steady‐state model for recharge to the well (the model assumes steady‐state radial flow to the well with rate dependent well drawdown and no storage effects) and that the ratio of change in LNAPL drawdown to change in LNAPL thickness at the well (d s /d b ) is constant. This ratio will be referred to as the j ‐ratio. Rather than having to meet boundary conditions for a predetermined j ‐ratio value, each baildown test provides the data to estimate the j ‐ratio value that is unique to that data set. This calculation methodology in turn results in the Bouwer‐Rice method being applicable to a wider range of baildown tests where it is not required for the potentiometric surface or LNAPL /water interface to remain constant.